This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Riboswitches are RNA domains that can regulate the expression of associated genes through the binding of a small molecule. The glycine riboswitch recognizes the amino acid glycine to upregulate expression of genes that allow glycine to be utilized as an alternative source of carbon. The most striking feature of this riboswitch is the fact that it can recognize glycine in a cooperative nature, allowing the regulated genes to transition from off to fully on with smaller changes in glycine concentration. The riboswitch is composed of two very similar aptamer domains linked by a short conserved region, and previous work in our lab has identified sections that are thought to be involved in cooperativity. To address the question of how cooperativity of ligand recognition is achieved in this RNA system we are working towards solving the crystal structure of the glycine riboswitch. To date, we have collected native data to approximately 3.6A. Our aims going forward focus on obtaining meaningful phase information and higher quality native data.